A power transmitting apparatus to transmit an engine power of a vehicle, such as an automobile etc., to the vehicle wheels requires not only transmission of the engine power to the wheels but enable radial and axial displacements and a moment displacement of the wheels caused by bounds of wheel or turning of vehicle during running on a rough road. Accordingly, an engine side (e.g. a transmission) and a wheel are connected via a drive shaft. One end is connected to a differential apparatus, via a slide type constant velocity universal joint. The other end is connected to a wheel via a wheel bearing apparatus that includes a secured type constant velocity universal joint.
Wheel bearing apparatus has evolved from a first generation type, using a single double row rolling bearing, to a second generation type, where an outer member is integrally formed with a body mounting flange. Furthermore, the wheel bearing apparatus has been developed from the second generation type to the third generation type. In the third generation type, one inner raceway surface of the double row rolling bearing is formed on the outer circumference of a wheel hub integrally formed with a wheel mounting flange. A fourth generation type includes the wheel hub integrally formed with a constant velocity universal joint. An outer joint member forming the constant velocity universal joint is formed, on its outer circumference, with the other inner raceway surface of the double row rolling bearing.
This application proposes a driving wheel bearing apparatus of the fourth generation type. The unit cover/joint assembly as well as the total assembly of the bearing apparatus for a driving wheel provided with the unit cover/joint assembly is shown in FIG. 9. In the description below, the term “outer side” (left hand side in the drawings) of the apparatus means a side that is positioned outside of the vehicle body. The term “inner side” (right hand side in the drawings) of the apparatus means a side that is positioned inside of the body when the bearing apparatus is mounted on the vehicle body.
The driving wheel bearing apparatus is formed as a unit including a wheel hub 51, a double row rolling bearing 52 and a constant velocity universal joint 53. The wheel hub 51 has a wheel mounting flange 54 at its outer side end. The wheel hub 51 is formed with an outer side inner raceway surface 51a on its outer circumference. Its inner circumference includes a hardened irregular portion 55.
The double row rolling bearing 52 includes an outer member 57, an inner member 58 and double row balls 56, 56. The outer member 57 has a body mounting flange 57b on its outer circumference. The body mounting flange 57b is mounted on a knuckle N and is formed with double row outer raceway surfaces 57a, 57a on its inner circumference. The inner member 58 has the wheel hub 51 and outer joint member 60 of the constant velocity universal joint 53 formed with inner side inner raceway surface 60a on its outer circumference.
The constant velocity universal joint 53 includes the outer joint member 60, a joint inner ring 61, cage 62, and torque transmitting balls 63. The outer joint member 60 has a cup shaped mouth portion 64, a shoulder portion 65 that forms a bottom of the mouth portion 64, and a hollow shaft portion 66 that axially extends from the shoulder portion 65. The shaft portion 66 is formed with a cylindrical portion 66a on its outer circumference. A fitting portion 66b axially extends from the cylindrical portion 66a. The wheel hub 51 and the outer joint member 60 are integrally connected, via plastic deformation, by inserting the shaft portion 66 into the wheel hub 51 and then by inserting an expanding tool, such as a mandrel, into the shaft portion 66 to radially expand the fitting portion 66b to bite into the irregular portion 55.
This driving wheel bearing apparatus is connected to a joint assembly JA. The joint assembly JA has a secured type (i.e. axially immovable type) constant velocity universal joint 53 that include the outer joint member 60. A drive shaft 67 has one end that is connected to the joint inner ring 61. A boot 68 is mounted on one end to the drive shaft 67 and on the other end to an opened side outer circumference of the outer joint member 60. A sliding type constant velocity universal joint 71 includes a boot 70. The boot 70 is mounted on one end to the drive shaft 67 and on the other end to an opened side outer circumference of the outer joint member 69. An outer diameter Da of the fitting surface 57c of the outer member 57 is formed larger than that of the constant velocity universal joint 53. An elastomer unit cover 72, of elastomer having a substantially cylindrical configuration and reduced diameter portions 72a, 72b at both of its ends, is mounted so that it covers the outer circumference of the joint assembly JA.
This structure not only protects the joint assembly JA but also enables easier handling during transportation. In addition the provision of the reduced diameter portions 72a, 72b at both ends of the unit cover 72 enables it to elastically mount onto the outer joint member 60 of the constant velocity universal joint 53. Thus, this prevents slipping off of the unit cover 72. Accordingly, it is possible to provide a joint assembly as well as a total assembly of a driving wheel bearing apparatus with the joint assembly that improves the workability in assembling it onto a body of vehicle and the quality of the bearing apparatus. (Japanese Laid-open Patent Publication No. 256938/2005)
However in the total assembly of a driving wheel bearing assembly of the prior art, since the unit cover 72 is formed as a monolithic structure, problems exist of requiring time not only of mounting the unit cover 72 to the joint assembly JA but also of demounting it therefrom without damaging the boot 68 after completion of mounting the total assembly of the driving wheel bearing apparatus to a body of the vehicle.